We propose to study development using the bacterium Myxococcus xanthus as a model system. Our specific objectives are: (a) To characterize myxobacterial hemagglutinin (MBHA), a development specific protein which peaks at the time of cellular aggregation. We plan to probe for the MBHA receptor in the cell membrane and in cell slime. (b) To isolate MBHA and protein S defective mutants of M. xanthus by direct screening of hundreds of developmental mutants in our collection. Mutants which are obtained will be characterized using biochemical, physiological and genetic techniques. (c) To continue mapping studies of aggregation defective mutants and attempt to assemble a large collection of mutants which are all genetically linked. The mutants will be analyzed. (d) To study transcriptional regulation of development. The RNA polymerase from vegetative and developmental extracts will be studied on several templates in order to study developmentally regulated transcription in vitro.